The present invention relates generally to electro-optical displays, and more particularly to selectively updating pulse width modulated waveforms that digitally drive display elements of a display device.
An array of display elements (e.g., pixels) in a display device may be driven using drive signals, such as modulated waveforms. In doing so, each modulated waveform may individually drive a different pixel of the display device. There are many ways to generate these drive signals. One approach involves using pulse width modulation (PWM) to form drive signals in display systems. By generating pulse width modulated waveforms, pixels with digital storage, such as in liquid crystal displays (LCDs) may be driven. For instance, a spatial light modulator (SLM) uses an electric field to modulate the orientation of a liquid crystal (LC) material. By the selective modulation of the LC material, an electronic display of an image may be produced on a screen, as the orientation of the LC material affects the intensity of light going through the LC material. Sandwiching of the LC material between an electrode and a transparent top plate, for example, may enable the modulation of the optical properties of the LC material. When the voltage applied across the electrode and the transparent top plate is changed, the LC material may produce different levels of output intensity, altering the image produced on the screen.
Typically, a display system includes a display device that receives data or content to be displayed in adjacent frames from a frame buffer memory within display refresh periods. More specifically, appropriate pixel data or value may be sent to each pixel. However, allowing a duty cycle of a drive signal to vary as a function of a pixel value within a display refresh period may result in multiple reads of display data, such as frame data from a frame buffer memory. While driving a pixel, several existing PWM-based schemes rely on an update of a PWM waveform based on an update of the pixel value, requiring large bandwidth between the frame buffer memory and pixel. Moreover, generation of such a frequently updated PWM waveform may not effectively control the LC material, resulting in a relatively poor quality display. Specifically, while displaying an image, this continuous updating of the PWM waveforms may result in numerous intermediate optical outputs from pixels that are being driven. That is, this technique may produce undesired, multiple, intermediate sub-levels of intensity while transitioning between different desired levels of intensity.
Thus, there is a need for better ways to controllably drive display elements in display systems with available digital storage.